The present invention relates to improvements in the type of concrete pumping apparatus disclosed in U.S. Pat. No. 4,198,193 to Westerlund et al. More particularly, the present invention seeks to provide a more effective and reliable means for biasing a wear ring on the oscillating valve assembly into firm sliding engagement at all times with the opposing wear plate of the hopper at the pump outlets. The invention also seeks to provide a better means of preventing the floating sleeve which biases the wear plate from becoming bound up or fouled by concrete which would eventually defeat the purpose and operation of the floating sleeve and also bind up the pump.
Additionally, the present invention seeks to utilize the pressure of the wet concrete on the floating sleeve to bias it in conjunction with or independently of hydraulic fluid pressure in the pump system so that failure of hydraulic pressure will not completely destroy the ability of the floating sleeve to hold the wear ring against the opposing wear plate.
The invention seeks further to improve and simplify the field serviceability of an apparatus of the general kind shown in the Westerlund patent.
Other features and advantages of the invention will become apparent during the course of the following detailed description.